Phenytoin is 5,5-diphenyl-2,4-imidazolidinedione. It is a well-known pharmaceutical agent having anticonvulsant and antiepileptic activity. Its preparation is described in U.S. Pat. No. 2,409,754.
Due to phenytoin's poor solubility in water, phenytoin sodium is employed in the preparation of injectable solutions of the drug. In order to stabilize solutions of phenytoin sodium, it is conventional to employ aqueous alcoholic solvent systems. Such solvent systems generally contain propylene glycol and/or other alcohols.
Even in the presence of alcoholic solvents, these solutions are unstable following dilution in intravenous fluids in that crystals form therein, precluding their safe use.
Thus, the need arose for stable aqueous preparation based on phenytoin, with or without solvents, which can be used in combination with one or more conventional intravenous fluid(s).